Abstract
BACKGROUND: Ductal carcinoma in situ (DCIS) is a non-invasive disease that rarely causes distant metastasis. It is extremely rare for patients diagnosed with DCIS without microinvasion to develop distant metastasis in the absence of ipsilateral or contralateral breast recurrence. This is the first case report of multiple liver and lung metastases from DCIS after breast-conserving surgery and radiotherapy. CASE PRESENTATION: A 45-year-old woman who was diagnosed with DCIS and received breast-conserving surgery, radiotherapy, and sequential endocrine therapy developed multiple metastases in the liver and lung despite not having bilateral breast recurrence at the 62-month follow-up. Comprehensive advanced breast cancer therapy was administered but did not prevent the progression of metastatic foci in the liver. CONCLUSIONS: This case shows the poor potential outcome in DCIS. Further research should be conducted on metastasis in DCIS; reexamination and monitoring are indispensable for patients diagnosed with DCIS.